Contribution of Single Photon Emission Computed Tomography to the Differential Diagnosis of Dementia in a Memory Clinic

Abstract

To evaluate the contribution of single photon emission computed tomography (SPECT) to the differential diagnosis of dementia, we studied 48 consecutive patients (median age: 63) with a degenerative or vascular dementia, a 99mTc-HMPAO SPECT imaging, and a diagnostic confirmation (autopsy or genetic mutation). The SPECT scans were visually rated by two nuclear medicine physicians (first blinded to the clinical data, then with the data). Comparisons between clinical diagnoses and/or SPECT imaging and neuropathology were performed. At the time of SPECT was performed, the clinical diagnosis of Alzheimer's disease (AD) sensitivity was 83%, specificity was 76%, and diagnostic accuracy was 79%. The blinded SPECT sensitivity was 57%, specificity 92%, and diagnostic accuracy 75%. The SPECT associated with clinical data sensitivity was 65%, specificity 84%, and accuracy 75%. The clinical diagnosis of frontotemporal-lobar degeneration (FTLD), progressive supranuclear palsy (PSP), and corticobasal degeneration syndrome (CBDs) sensitivity was 83%, specificity 87%, and accuracy 85%. The blinded SPECT sensitivity was 50%, specificity 97%, and accuracy 79%. The SPECT associated with clinical data sensitivity was 61%, specificity was 93%, and accuracy 81%. Whenever the blinded SPECT interpretation agreed with the clinical diagnosis of AD and FTLD/PSP/CBDs, the condition was confirmed by neuropathological assessment in all cases. Compared with clinical diagnosis alone, SPECT imaging improved the specificity of the etiological diagnosis in degenerative dementia, although its sensitivity was not as good as that of clinical diagnosis. For AD and FTLD/PSP/CBDs, agreement between the clinical and SPECT-based diagnoses was always confirmed by neuropathological assessment.